GCN Circulars
GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search
To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.
Advanced Search Examples (click to copy):
subject:"Swift"body:"GRB"submitter:"Judith Racusin"26336 results found.
- Konus-Wind detection of GRB 260617A
- GRB 260616B: AstroSat CZTI detection
- GRB 260616A: AstroSat CZTI detection
- GRB 260616A: SVOM/GRM observation
- EP260618a: OHP/T193 optical observations
- GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
- GRB 260619A: Kilonova-Catcher optical upper limit
- EP260618a: LCO optical counterpart confirmation
- GRB 260617A: CALET Gamma-Ray Burst Monitor detection
- EP260618a: COLIBRÍ optical counterpart candidate
- GRB 260616A: NuSTAR detection of prompt emission
- GRB 260614B: NuSTAR detection of prompt emission
- GRB 260619A: SVOM possible detection of a faint burst
- GRB 260618B: Fermi-LAT detection
- IPN triangulation of GRB 260617A (short)
- GRB 260616A: Insight-HXMT detection
- EP260618a: EP-WXT detection of an X-ray transient
- GRB 260506B: cubesat Avion detection
- GRB 260616C: GECAM-B observation of a burst
- GRB 260617A: Fermi GBM Detection
- GRB 260616A: Fermi GBM Observation
- Konus-Wind detection of GRB 260616B/EP260616a
- Konus-Wind detection of GRB 260616A
- GRB 260616B: CALET Gamma-Ray Burst Monitor detection
- EP260616a/GRB260616B: COLIBRÍ optical upper limit
- GRB 260616A: GECAM-B observation
- GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
- GRB 260429A: cubesat Avion detection
- GRB 260616A: Fermi-LAT detection
- GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
- GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
- GRB 260614A: AstroSat CZTI detection
- EP260616a: EP-WXT detection of a fast X-ray transient
- GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations
- GRB 260616B: Fermi GBM Detection
- GRB 260604C: GRANDMA late observations with CFHT/MegaCam
- GRB 260614B: SVOM/ECLAIRs refined analysis
- GRB 260614B: GECAM-B observation
- GRB 260610B: SVOM/GRM observation
- GRB 260614B: SVOM/VT optical afterglow confirmation
- GRB 260614B: Fermi GBM Observation
- GRB 260614A: GECAM-B observation
- GRB 260614B: SVOM/VT optical candidate from VHF data
- GRB 260614B: SVOM detection of a burst
- GRB 260611B: SVOM/GRM detection
- GRB 260603C: AstroSat CZTI detection
- GRB 260610B: further Liverpool Telescope optical observations
- GRB 260610B: Fermi GBM Observation
- GRB 260610B / AT2026owq: GRANDMA optical observations
- GRB 260610B / AT2026owq: further SAO RAS optical observations
- EP260605a: COLIBRÍ optical upper limits
- GRB 260610b: Liverpool Telescope optical observations
- IceCube-260610A: No candidates from the Zwicky Transient Facility
- GRB 260611B: CALET Gamma-Ray Burst Monitor detection
- The EP-WXT trigger 01709269176: SVOM/C-GFT confirmation of a stellar flare
- GRB 260610B / AT2026owq: SVOM/VT optical observations
- GRB 260610B / AT2026owq: SAO RAS optical observations
- GRB 260610B: optical counterpart shows spectroscopic redshift of z=0.473
- EP260610b: refined analysis of the EP-WXT and follow-up EP-FXT observations
- GRB 260610B / AT 2026owq: COLIBRÍ optical observations
- GRB 260610B / AT2026owq: Early ATLAS observations
- GRB 260610B: TRT optical observation
- EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
- EP260610b: COLIBRÍ optical observations
- GRB 260610B: DDOTI optical observations
- EP260610b: MAO/AZT-22 optical observations
- GRB 260610B: GOTO optical counterpart candidate
- EP260610b: NOT optical observation
- EP260610b: SVOM/VT optical confirmation with blue color
- IceCube-260610A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 260515A: SOAR optical observations
- EP260610b: Gemini North optical counterpart candidate
- EP260610a: SVOM/VT optical upper limits
- EP260610b: Einstein Probe detection of an X-ray transient
- Konus-Wind detection of GRB 260601A
- IPN triangulation of GRB 260601A (short/hard)
- EP260610a: COLIBRÍ optical upper limits
- EP260610a: Einstein Probe detection of a fast X-ray transient
- Konus-Wind detection of GRB 260604C
- GRB 260608A: Fermi GRB Observation
- GRB 260604C: AstroSat CZTI detection
- IPN triangulation of GRB 260601B / EP260601a
- GRB 260604C: SVOM/ECLAIRs refined analysis
- GRB 260608A: SVOM/ECLAIRs refined analysis
- Konus-Wind detection of GRB 260607B
- GRB 260607B: GECAM-B observation
- GRB 260604C: further SAO RAS optical observations
- GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
- GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
- GRB 260604C: SVOM/C-GFT upper limit
- GRB 260607B: AstroSat CZTI detection
- GRB 260608A: SVOM detection of a burst
- EP260605a: EP-FXT follow-up observation
- GRB 260607A: TRT optical observations
- GRB 260604C: GRANDMA further observations
- GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
- GRB 260604A: SVOM/GRM detection
- GRB 260607B: Fermi GBM Observation
- GRB 260607B: Fermi-LAT detection
- GRB 260607B: Fermi GBM Final Localization Correction